Okay... endgame Elsa from a parallel save file or New Game +. Assuming that older Elsa is a regressor trying to save Yvonne, then there's a good chance the fake Yvonne seen in the Villainess System regressed as well.
Looks like Yvonne already was fated to suffer when she was young. If the little girl witch-Elsa wanted to protect in the past and future is truly the same person as the sadist Yvonne from another storyline, it raises the question why she stayed gentle rather than became a psychopath in this lifetime. Her memories of being a commoner on Earth also make time travel even more confusing.